Hi, I'm currently packaging a robotics simulator called Morse
( https://bugzilla.redhat.com/show_bug.cgi?id=770740 ). Morse allows its
simulations to be interacted with via multiple middleware protocols,
including sockets, YARP, pocolibs, ROS, and a few others. Upstream has
recommended that I extract support for these protocols into separate
subpackages, which seems very reasonable. Unfortunately, it doesn't seem
that we have packages for some of these middlewares.
Any advice would be much appreciated.

We had a similar issue for the packaging of SOCI (
http://soci.sourceforge.net,
https://admin.fedoraproject.org/pkgdb/acls/name/soci), which is an
abstraction layer on top of third-party database back-ends/libraries,
including some not well supported by Fedora or even proprietary (Oracle).
So, we used "%bcond_with oracle" rules, translating into "--with/--without
oracle" options on the rpmbuild command-line. You can have a look at the
RPM specification file:
http://pkgs.fedoraproject.org/gitweb/?p=soci.git;a=blob_plain;f=soci.spec...
more details. In other terms, while mainstream Fedora does not provide
the Oracle sub-package, anyone can easily build the RPM if he/she has all
the necessary software stack and rights to use on his/her environment.
Hope it helps.
Kind regards
Denis